Tidal current energy generating device

ABSTRACT

A tidal current energy generating device includes an outer frame ( 1 ), at least two inner frames ( 2 ), at least two mounting shafts ( 4 ), a driving unit ( 6 ), at least four horizontal-axis hydraulic generators ( 3 ), and at least six bearings ( 5 ). The at least two inner frames ( 2 ) are separably disposed in the outer frame ( 1 ), respectively. The at least two mounting shafts ( 4 ) are rotatablely disposed in the two inner frames ( 2 ), respectively, and the axial direction of the at least two mounting shafts ( 4 ) is perpendicular to the horizontal plane. The driving unit ( 6 ) is connected with the at least two mounting shafts ( 4 ) to drive the mounting shafts ( 4 ) to rotate. Every two horizontal-axis hydraulic generators ( 3 ) are fixed at one mounting shaft ( 4 ) and are disposed in the same inner frame ( 2 ). The at least four horizontal-axis hydraulic generators ( 3 ) change directions with the rotating of the mounting shaft ( 4 ). Every three bearings ( 3 ) are sleeved on one mounting shaft ( 4 ), and the three bearings ( 5 ) on one mounting shaft ( 4 ) are disposed on the two sides and the center of the two horizontal-axis hydraulic generators ( 3 ), respectively. The tidal current energy generating device can be maintained or replaced conveniently and can extend deeply in the sea.

TECHNOLOGY FIELD

This invention relates to a generating device and, more particularly, to a tidal current energy generating device.

BACKGROUND ART

Ocean energy (including tidal energy, tidal current energy, ocean wave energy, and ocean current energy) refers to mechanical energy generated by the flowing of sea water. As a kind of renewable energy, the ocean energy has great development prospect and value due to its abundant reserve and wide distribution. The primary use of the ocean energy is for power generation. The working principle of ocean energy power generation is similar to that of wind power generation. That is, the mechanical energy of the sea water is converted into electric energy by energy conversion devices. Specifically, at first, the sea water impacts hydro turbines, the hydro turbines convert the energy of the water flow into the mechanical energy of rotation, and then the hydro turbines drive power generators to generate power via mechanical drive systems, thereby finally converting the mechanical energy to the electric energy.

Nowadays, with the increasing shortage of energy and the increasing serious green house effect, energy is required to be low-carbon. Thus, clean energy, such as wind energy and the ocean energy, is the future direction of energy development. However, the power generating devices for the clean energy are still developing, and the utilization of the ocean energy is still in an initial stage, except the relatively mature wind energy utilization. No general-purpose and proven devices are available. The efficiency is relatively low, and it is difficult to realize large-scale devices.

Since the ocean environment is complicated and the water resistance is large, the installation of the conventional ocean energy power generator in the ocean has great difficulties and needs large costs. In addition, since the power generator contacts the sea water over a long period of time, under long corrosion and huge impaction of the sea water, the ocean energy power generator needs regular maintenance or replacement after being used for a period of time. However, the maintenance and replacement of the conventional ocean energy power generator are also carried out in the ocean, and thus the difficulty is high and the cost is huge. Even the whole ocean energy power generator will be scraped only due to the damage of some components, which is one important reason causing the high cost of the ocean energy power generator and is also a direct reason causing the conventional ocean energy power generator failing to realize large-scale and commercialized operation.

In particular, since the whole horizontal-axis hydraulic generator (including an impeller and a generator) is under water, the maintenance and repair of the horizontal-axis hydraulic generator is more difficult, and the cost is much higher. Thus, even though the power generating efficiency of the horizontal-axis hydraulic generator is higher than that of the vertical-axis hydraulic generator, the horizontal-axis hydraulic generator still fails to achieve commercialization. However, those skilled in the ocean energy power generating field have overlooked the improvement of the modes of installing and repairing.

In addition, the tidal current energy utilizes the tidal current in the ocean to generate electricity, and the direction of the tidal current changes along with the flood and ebb tides. More important, the speed of the tidal current is not constant. When a generating device is installed, once a generator is chosen, the load thereof is determined. However, as the speed of the tidal current is not constant, the generating capacity is not constant. In order to save the cost and subject to technology limitations, the existing ocean energy generating device can only carry a power generation load below a certain current speed, no matter the generator is the horizontal-axis hydraulic generator or the vertical-axis hydraulic generator. Once the current speed increases, the power generating capacity exceeds the load, and the generator will be overloaded and easily damaged. Therefore, to extend the working life of the generator, the conventional ocean energy generating device has to cut off the current completely to stop the generator once the tidal current exceeds a certain speed.

Another ocean energy generating device utilizing the horizontal-axis hydraulic generator learns from the design of the wind-driven generator, which adjusts the load of the generating device by varying the pitch. When the water flow is relative large, the blade angle of attack is reduced by an adjusting device; when the water flow is relative small, the blade angle of attack increases by the adjusting device. However, this design has a major drawback. Different from the environment conditions where the wind-driven generator is used, the horizontal-axis hydraulic generator is used in the water, and the resistance to which it is subjected is far greater than the resistance to which the wind-driven generator is subjected. In addition, as the blade angle of the horizontal-axis hydraulic generator is the object to be adjusted and the rotating mechanism is entirely in the water, a close degree for installing between every blade component is needed to be designed accurately to achieve the rotation of the blade angle. If the connection is very tight, the friction force will be too large, and it is difficult to adjust the upstream face angles of the blades, resulting in a failed adjusting effect of the adjusting device. Under this condition, the generating device cannot improve the efficiency when the water flow is too small and cannot really protect the generator when the water flow is too large. If the connection is too loose, the friction force will be too small, and although the adjusting is very easy, there will be a serious problem of loss of sealing. Therefore, the water flow will be injected into the inner of the impeller and destroy the entire impeller, greatly increasing the maintenance rate and sharply increasing the cost.

On the other hand, for the generating device utilizing ocean energy, especially the tidal current energy, to generate electricity, the rotating shaft thereof bears a huge impact force exerted by the water flow in the radial direction. After a period of time, the seal ring between the rotating shaft and a conventional bearing is easily deformed, and the sealing of the bearings cannot be ensured. Since the problem of high sealing requirements cannot be solved, the existing ocean energy generating device has to abandon rolling bearings with the oil as a lubricant and can choose sliding bearings which use the water as the lubricant. However, those skilled in the art have ignored one problem. The water that can be used as the lubricant must be pure water. In other words, as the water flow usually contains a lot of sediments, if the external water carrying impurities such as sediments flows into the bearing because of the elastic deformation of the sealing rings, not only cannot achieve the lubrication effect to the bearing, but also the normal work of the rotating shaft is affected, and ultimately the generating efficiency of the generating device is affected.

All the existing ocean energy generating devices cannot solve the problem how to improve the sealing of the bearings under the water. Therefore, the rotation device designed to control the blade or the generator is very complex and cannot be singly adjusted by one rotating shaft.

SUMMARY OF THE INVENTION

To overcome at least one deficiency in the prior art, this invention provides a tidal current energy generating device.

To achieve the above objective, this invention provides a tidal current energy generating device, including an outer frame, at least two inner frames, at least two mounting shafts, a driving unit, at least four horizontal-axis hydraulic generators, and at least six bearings. The at least two inner frames are separably disposed in the outer frame. The at least two mounting shafts are rotatablely disposed in the two inner frames, respectively, and an axial direction of the at least two mounting shafts is perpendicular to a horizontal plane. The driving unit is connected with the at least two mounting shafts to drive the mounting shafts to rotate. Every two horizontal-axis hydraulic generators are fixed at one mounting shaft and are disposed in the same inner frame. The at least four horizontal-axis hydraulic generators change their directions with the rotating of the driving unit. Every three bearings are sleeved on one mounting shaft, and the three bearings on one mounting shaft are disposed on the two sides and the center of the two horizontal-axis hydraulic generators, respectively.

In an embodiment of the invention, the tidal current energy generating device may further comprise at least four water flow deflectors. Every water flow deflector may be disposed corresponding to every horizontal-axis hydraulic generator, and the at least four water flow deflectors may be fixed at the outer frame or the inner frames. Every water flow deflector may have two water guiding sections and one middle section, and the middle section may be located between the two water guiding sections. A cross section of one side of every water guiding section far away from the middle section may be rectangular, a cross section of one side of every water guiding section connected with the middle section may be circular, and a cross section of the middle section may be circular. The cross sections may be perpendicular to the horizontal plane and may be perpendicular to the water flow direction, and the area of the circular cross section may be smaller than that of the rectangular cross section.

In an embodiment of the invention, the tidal current energy generating device may further comprise an underwater shaft rotating protecting device, wherein the underwater shaft rotating protecting device may comprise a lubricant storage tank, at least six seal rings, and a tube. A lubricant may be stored in the lubricant storage tank, and the lubricant storage tank may be disposed above the water surface. Every two seal rings may correspond to one bearing and are sleeved on the mounting shaft, and a lubricant cavity may be formed between every two seal rings and the corresponding bearing and the mounting shaft. One end of the tube may be communicated with the lubricant storage tank, and the other end may be communicated to the lubricant cavity.

In an embodiment of the invention, the underwater shaft rotating protecting device may further comprise a detection module, and the detection module may be disposed at the lubricant storage tank to detect whether the lubricant is reduced or not.

In an embodiment of the invention, the bearing may be a sliding bearing, and every lubricant cavity may be formed by two seal rings, the bearing, and the mounting shaft.

In an embodiment of the invention, the bearing may be a rolling bearing, the underwater shaft rotating protecting device may further comprise at least three bearing houses, and each lubricant cavity may be formed by two seal rings, the bearing, the bearing houses, and the mounting shaft.

In an embodiment of the invention, the outer frame may have a plurality of fixed piles, and the outer frame may be fixed at the sea bottom through piling.

In an embodiment of the invention, the outer frame may have a plurality of reducing water flow resistance structures.

To sum up, the tidal current energy generating device in the invention can allow the generating device to be modularly assembled and replaced above the water surface by disposing separable inner frames and the outer frame, such that the costs of maintenance and installation can be greatly reduced, thereby overcoming the difficulties that the conventional ocean energy generating device cannot be commercialized and large-scale. Further, by disposing at least two horizontal-axis hydraulic generators and at least three bearings on the mounting shaft, the “multipoint restriction” is achieved for the mounting shaft, which makes the scale of the tidal current energy generating device can be extended not only in the horizontal direction (the horizontal direction perpendicular to the water flow) but also in the vertical direction (the depth direction perpendicular to the horizontal plane), such that the power generation efficiency is greatly improved and the problem that the existing ocean energy generating devices cannot “be large” and “be deep” is solved. By disposing the mounting shaft, the load of the generator can be innovatively adjusted by changing the orientation of the entire horizontal-axis hydraulic generator instead of individually changing the direction of the upstream angles of the blades, so that no matter how much the current speed is, the generator can always be guaranteed to be in a safe load and generate electricity, thereby greatly improving the power generation efficiency. More important, by disposing a rotatable mounting shaft, the impeller of the horizontal-axis hydraulic generator can always be turned towards the water flow regardless of the direction in which the water flows, thereby ensuring the maximum generating power, which is especially suitable for utilizing the tidal energy to generate power.

By disposing the water flow deflectors, the water flows are all concentrated to the horizontal-axis hydraulic generator, making the impeller of the horizontal-axis hydraulic generator subject to a larger force and rotate faster, and thus the power generation efficiency is improved. The water flow deflector provided by the embodiments of the invention is rectangular at the two ends and circle in the middle, and it can always achieve the flow guiding function regardless of the flood tide or the ebb tide. Further, the water flow deflector with a specific structure has a better flow guiding effect.

In addition, the underwater shaft rotating protecting device provided by the invention can effectively protect the bearings from the outer impurities, especially preventing the sediments in the water from entering into the bearings, so as to effectively protect the normal operation of the bearings. By adopting the underwater shaft rotating protecting device, the tidal current energy generating device in the invention extends the service lives of the bearings, the maintenance frequency and maintenance costs are greatly reduced, and the power generating efficiency is ensured not to be affected at the same time. Furthermore, the bearing of the tidal current energy generating device provided by the invention can be a rolling bearing, which overcomes the technical barrier that only sliding bearing with water as the lubricant can be used for an underwater shafting in the prior art.

Moreover, by setting the detection module, whether the sealing of the bearings is reduced or not can be known intuitively and timely, which effectively guides the maintenance personnel when and where to maintain, thereby improving the promptness and reliability of the maintenance. In addition, since the frame includes separable outer frame and inner frame, the underwater shaft rotating protecting device can be maintained or replaced conveniently and quickly, and the maintenance cost is greatly reduced.

These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a built-in module of a tidal current energy generating device provided by the first embodiment of the invention;

FIG. 2 is an enlarged schematic diagram of the circle mark V in FIG. 1;

FIG. 3 is a schematic diagram of a built-in module of a tidal current energy generating device provided by the second embodiment of the invention;

FIG. 4 is a top view of a tidal current energy generating device provided by the third embodiment of the invention;

FIG. 5 is a front view of the tidal current energy generating device provided by the third embodiment of the invention;

FIG. 6 is an enlarged schematic diagram of the circle mark U in FIG. 5;

FIG. 7 is a structural schematic diagram of a water flow deflector provided by the third embodiment of the invention; and

FIG. 8 is a front view of the water flow deflector provided by the third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram of a built-in module of a tidal current energy generating device provided by the first embodiment of the invention FIG. 2 is an enlarged schematic diagram of the circle mark V in FIG. 1. Please refer to FIG. 1 and FIG. 2 together. The tidal current energy generating device provided by the embodiment includes an outer frame 1, at least two inner frames 2, at least four horizontal-axis hydraulic generators 3, at least two mounting shafts 4, at least six bearings 5, and a driving unit 6.

FIG. 1 only shows one built-in module 100 of the tidal current energy generating device, and therefore only one inner frame 2, two horizontal-axis hydraulic generators 3, one mounting shaft 4, three bearings 5 and the driving unit 6 are displayed. The tidal current energy generating device of the invention includes at least two built-in modules 100.

At least two inner frames 2 are separably disposed in the outer frame 1. In the embodiment, a hook may be disposed in the inner frame 2 (not shown in the figure), an engaging slot may be disposed in the outer frame 1 (not shown in the figure), and the inner frame 2 is embedded into the outer frame 1 by the hook and the engaging slot interlocking together. However, the mounting mode of the inner frame 2 and the outer frame 1 in the invention is not limited,

One inner frame 2, at least two horizontal-axis hydraulic generators 3, at least one mounting shaft 4, and at least three bearings 5 form a built-in module 100. In actual application, at least two horizontal-axis hydraulic generators 3, at least one mounting shaft 4, and at least three bearings 5 can be disposed in one inner frame 2 at first, and then at least two assembled frame 2 is fixed in the outer frame 1, thus to achieve the modular installation of the tidal current energy generating device. In detail, the built-in module 100 can be installed ashore, and then the built-in module 100 is hanged into the outer frame 1 in the ocean and is fixed to the outer frame 1, thereby greatly simplifying installing procedures, reducing installing time, and reducing installing difficulties in the ocean.

The number of the inner frames 2 is not limited in the invention. In actual application, the number of the inner frames 2 may be as much as twelve. At least two inner frames are separably disposed in the outer frame, which breaks through the drawback that the existing ocean tidal current energy generating device cannot realize a large scale. By now the generating capacity of a single unit of the largest ocean tidal current energy generating device in the world is 1.2 MW, however, the generating capacity of a single unit of the tidal current energy generating device in this invention is 5 MW, which is much higher than the largest generating capacity of the existing ocean tidal current energy generating device.

The horizontal-axis hydraulic generator 3 includes an impeller 31 and a generator 32 (as shown in FIG. 3). As the horizontal-axis hydraulic generators 3, the impeller 31, and the generator 32 are all under the water, if the horizontal-axis hydraulic generators 3 fails, the conventional ocean current energy generating device needs to be repaired in the sea. Thus, the maintenance is very difficult, and the cost is quite high. However, for the tidal current energy generating device in the invention, the built-in module 100 can be directly taken out of the sea to be maintained or replaced, thereby realizing quick replacement and maintenance of the tidal current generating device 100 above the water surface and greatly reducing the maintenance cost, such that the commercialization of the tidal current generating device 100 can be realized.

At least two mounting shafts 4 are rotatablely disposed in the two inner frames 2, respectively. An axial direction X of the mounting shafts 4 is perpendicular to a horizontal plane P. Every two horizontal-axis hydraulic generators 3 are fixed at one mounting shaft 4 and are disposed in the same inner frame 2. At least four horizontal-axis hydraulic generators 3 change their directions with the rotating of the mounting shafts 4. The driving unit 6 is connected to the mounting shaft 4 and drives the mounting shaft 4 to rotate. As the water flow directions of the flood and ebb tides are opposite, no matter which direction the water flow comes towards, the impeller 31 of the horizontal-axis hydraulic generators 3 controlled by the rotating of the mounting shafts 4 is always towards the water flow, thus to improve the using rate of the tidal current energy and improve the efficiency of power generation.

In actual application, when the water flow moves towards the tidal current energy generating device along the water flow direction shown in FIG. 4, the driving unit 6 doesn't work. At that time, the impeller 31 of the horizontal-axis hydraulic generators 3 faces the water flow. When the water flow moves towards the tidal current energy generating device along a direction opposite to the flow direction (from top to bottom in FIG. 3), the driving unit 6 drives the mounting shaft 4 to rotate, and thus drives the horizontal-axis hydraulic generators 3 to rotate 180 degrees, such that the impeller 31 is upturned from facing downward to make sure that the impeller 31 of the horizontal-axis hydraulic generators 3 always faces the water flow. This situation is especially suitable for utilizing the tidal current energy to generate power, which ensures the maximum power generating efficiency.

Especially, in actual application, the water flow directions of the flood and ebb tides are not exactly parallel, and are not definitely perpendicular to an upstream face of the horizontal-axis hydraulic generators 3. No matter which direction the water flow comes towards the horizontal-axis hydraulic generators 3, the orientation of the horizontal-axis hydraulic generators 3 can be controlled by the mounting shafts 4 of the tidal current energy generating device in the invention, thus to maximize the utilization of the tidal current energy and improve the generated power.

In addition, when the actual water flow rate is larger than the rated speed corresponding to the maximum load of the horizontal-axis hydraulic generators 3, at that time, it is only needed to rotate the horizontal-axis hydraulic generators 3 off the water flow direction in a certain angle by the mounting shaft 4, so that the load of the horizontal-axis hydraulic generators 3 can be effectively reduced. The horizontal-axis hydraulic generators 3 is ensured not to be destroyed due to the overload, and the horizontal-axis hydraulic generators 3 can still be ensured to work normally and output the generated electricity continuously and stably, which overcomes the deficiency that the generator stops working in order to avoid burning when the water flow rate is too large. At the same time, pitch adjustment is not needed, making the load adjustment of the generator more simple and effective. When the actual flow rate is less than the rated speed corresponding to the maximum load of the horizontal-axis hydraulic generators 3, it is only needed to rotate the mounting shaft 4 to control the horizontal-axis hydraulic generators 3 to rotate to face the water flow direction (that is, the upstream face of the horizontal-axis hydraulic generators 3 is perpendicular to the water flow direction). Thus, the water flow can be utilized to a maximum extent to generate electricity, thereby improving the generated power.

In the embodiment, the number of the inner frames 2 is equal to that of the mounting shafts 4, and the number of the horizontal-axis hydraulic generators 3 is the double of that of the mounting shafts. However, this invention is not limited thereto. In other embodiments, one built-in module 100 can have a plurality of mounting shafts 4 and each of the mounting shafts 4 can have more than two horizontal-axis hydraulic generators 3.

In the embodiment, the number of the driving units 6 corresponds to the number of the mounting shafts 4 and is at least two. However, this invention is not limited thereto. In other embodiments, a gear or other transmission mechanism can be utilized to achieve the control of two mounting shafts 4 by one driving unit 6. Each driving unit 6 includes a motor 61 and a transmission mechanism 62, the transmission mechanism 62 is connected with one end of the mounting shaft 4 (the upper end in FIG. 1), the motor 61 rotates drives the mounting shaft 4 to rotate by the transmission mechanism 62. In the embodiment, the transmission mechanism 62 includes a driving gear and a driven gear engaged with the driving gear. The motor 61 drives the driving gear to rotate, thus to drive the driven gear to rotate. A gear hole of the driven gear is close fit to the upper end of the mounting shaft 4 to drive the mounting shaft 4 to rotate. However, this invention is not limited thereto. In other embodiments, the driving unit may include a motor and a reducer. As the existing motor generally rotates fast, the rotation speed can be greatly reduced by the reducer thus to control the rotation speed and rotation range of the mounting shaft 4 effectively and accurately.

Every three bearings 5 are sleeved on one mounting shaft 4. As shown in FIG. 1, the two bearings 5 on one mounting shaft 4 are disposed on the two sides of the two horizontal-axis hydraulic generators 3, respectively, and one bearing 5 is disposed between the two horizontal-axis hydraulic generators 3.

By disposing two or more horizontal-axis hydraulic generators 3 in a depth direction D1, the depth of the tidal current energy generating device 100 in the depth direction D1 can be greatly expanded, such that the tidal current energy can be utilized more efficiently to generate power. By disposing at least three bearings 5 on one mounting shaft 4 to achieve the “multipoint restriction” to the mounting shaft 4, no matter how long the mounting shaft 4 is made, under the huge impact force of the sea water, the three bearings 5 share the stress and meanwhile provide the fixing and support for the mounting shaft 4 by at least three points, making the length of the mounting shaft 4 no more limited. Thus, more horizontal-axis hydraulic generators 3 can be installed in the depth direction D1, and the scale of the tidal current energy generating device can be greatly expanded, thereby improving the generation power and solving the technical problem that the tidal current energy generating device in the prior art cannot be made deep in the sea.

In the embodiment, the tidal current energy generating device further includes an underwater shaft rotating protecting device 7, and every underwater shaft rotating protecting device 7 comprises a lubricant storage tank 71, at least six seal rings 72, and a tube 73. The lubricant 74 is stored in the lubricant storage tank 71, and the lubricant storage tank 71 is disposed above the water surface P. Every two seal rings 72 correspond to one bearing 5 and are sleeved on the mounting shaft 4, and a lubricant cavity 75 is formed between every two seal rings 72 and the corresponding bearing 5 and the mounting shaft 4. One end of the tube 73 is communicated with the lubricant storage tank 71, and the other end is communicated with the lubricant cavity 75.

In the embodiment, the number of the tubes 73 and the lubricant storage tanks 71 in each built-in module 100 are both two, and the two tubes 73 are communicated with the two sides of the lubricant cavity 75 and the two lubricant storage tanks 71, respectively. The speed of filling with the lubricant 74 is improved by increasing the number of the tubes 73. However, this invention is not limited thereto. In the embodiment, the tube 73 may be made of stainless steel.

In the first embodiment, the bearing 5 is a sliding bearing, every lubricant cavity 75 is formed by two seal rings 72, the bearings 5, and the mounting shaft 4. In detail, upper and lower surfaces of the lubricant cavity 75 are formed by the two seal rings 72, respectively, the inner surface of the lubricant cavity 75 is the outer surface of the journal portion of the mounting shaft 4, and the outer surface of the lubricant cavity 75 is the inner surface of the bearing 5. A cross section of the lubricant cavity 75 is annular, and the longitudinal section is a rectangular annular cylinder. The lubricant 74 is filled in the lubricant cavity 75 to form a lubricant film thus to reduce the friction. In the first embodiment, the lubricant 74 is pure sea water without impurities such as sediments and so on.

As the impact force of the tidal current to the mounting shaft 4 is huge, the seal ring 72 is subjected to a huge radial force for a long period of time and is easy to be elastically deformed, which leads to no further sealing between the seal ring 72 and the mounting shaft 4. That is, a gap is formed between the seal ring 72 and the mounting shaft 4. Since the lubricant 74 is originally located in the lubricant cavity 75, when a gap exists in the lubricant cavity 75, the lubricant 74 may run off, meanwhile, the water outside will carry the impurities such as sediments to flow in from the gap.

The following details how the underwater shaft rotating protecting device 7 for tidal current energy generating provided by the embodiment protects the mounting shaft 4 under the water surface.

Since the lubricant storage tank 71 is located above the water surface P, while the connection section of the horizontal-axis hydraulic generator 3 and the mounting shaft 4 is under the water surface P, there is a height difference between them. According to the fluid pressure formula, the pressure is in direct proportion to the depth (the height between the pressure measuring point and the liquid level). Since the lubricant 74 located within the lubricant cavity 75 is conveyed by the tube 73 communicated with the lubricant storage tank 71, in the case that the density is the same, the pressure where the lubricant cavity 75 is communicated with the tube 73 is definitely larger than the outer pressure at the same depth. Meanwhile, as the liquid can transmit the pressure, the inner pressure on the sealing point of the seal ring 72 must be larger than the outer pressure on the sealing point of the seal ring 72. Therefore, the lubricant cavity 75 is always in a state of “micro-positive pressure”.

In other words, even though the sealing between the bearing 5 and the mounting shaft 4 cannot be realized, namely, a gap exists between the seal ring 72 and the mounting shaft 4, the lubricant 74 will also continually flow from the lubricant storage tank 71 into the lubricant cavity 75 due to the pressure difference action, and then flows from the gap to the outside of the seal ring 72, and the outer water with sediments won't flow into the lubricant cavity 75 from the gap, so that the protection for the mounting shaft 4 can be truly achieved.

In actual application, the tube 73 further includes a joint, and multichannel configuration can be achieved by the joints, such that the lubricant cavity 75 in the three bearings 5 can share a master route of one tube 73 to communicate the common lubricant storage tank 71. However, this invention is not limited thereto.

In the embodiment, the underwater shaft rotating protecting device 7 for tidal current energy generating further includes a detection module 76, which is disposed at the lubricant storage tank 71 to detect whether the lubricant is reduced or not. In actual application, the detection module 76 may be an infrared sensor, detecting whether the height of the lubricant 74 in the lubricant storage tank 71 is reduced or not to judge whether the lubricant 74 is reduced. The detection module 76 may also be a gravity sensor, detecting whether the weight of the lubricant 74 in the lubricant storage tank 71 is reduced or not to judge whether the amount of the lubricant 74 changes. The reduction of the lubricant 74 represents a decrease in the sealing performance of the bearing 5, thereby reminding the maintenance personnel that the seal ring 72 has been aged or deformed and needs to be repaired or replaced. By setting the detection module 76, the maintenance personnel can know the states of the shafting intuitively and timely, especially the working state of the seal ring 72, and maintain the tidal current energy generating device in time.

In actual application, the underwater shaft rotating protecting device 7 may further include an alarm module (not shown in the figure), and the alarm module is connected to the detection module 76. When the detection module 76 detects that the lubricant 74 decreases, the alarm module raises the alarm.

FIG. 3 shows a schematic diagram of a built-in module of the tidal current energy generating device provided by the second embodiment of the invention. In the second embodiment, structures and functions of the outer frame 1, the inner frames 2, the horizontal-axis hydraulic generator 3, the mounting shaft 4, the bearing 5, and the driving unit 6 are all the same as those described in the first embodiment, and the same elements are referenced with the same numbers, which are not described herein for a concise purpose. Only the differences are described hereinafter.

In the embodiment, four horizontal-axis hydraulic generators 3 are fixed at one mounting shaft 4. Two of the three bearings 5 are disposed on the upper and lower sides of the horizontal-axis hydraulic generator 3 on the mounting shaft 4, and the other one is disposed between every two horizontal-axis hydraulic generators 3. In other words, take two horizontal-axis hydraulic generators 3 as a group to ensure the bearing 5 is disposed between every group of the horizontal-axis hydraulic generators 3. A multipoint restriction and support for the mounting shaft 4 can still be achieved by such setting.

FIG. 4 is a top view of a tidal current energy generating device provided by the third embodiment of the invention. FIG. 5 is a front view of the tidal current energy generating device provided by the third embodiment of the invention. FIG. 6 is an enlarged schematic diagram of the circle mark U in FIG. 5. FIG. 7 is a structural schematic diagram of the water flow deflector provided by the third embodiment of the invention. FIG. 8 is a front view of the water flow deflector provided by the third embodiment of the invention. Please refer to FIG. 4 to FIG. 8 together.

In the third embodiment, structures and functions of the inner frames 2, the horizontal-axis hydraulic generator 3, the mounting shaft 4, the bearing 5, and the driving unit 6 are all the same as those described in the first embodiment, and the same elements are referenced with the same numbers, which are not described herein for a concise purpose. Only the differences are described hereinafter.

An outer frame 1′ can be made by welding steel material. In the embodiment, the outer frame 1′ includes an outer sleeve 11 and a fixed pile 12. The fixed pipe 12 is formed by pouring of concrete in the outer sleeve 11. The outer frame 1′ is fixed at the sea bottom F through piling.

In the embodiment, the outer frame 1′ further comprises a plurality of reducing water flow resistance structures 13. The multiple reducing water flow resistance structures 13 are disposed on the upstream side of the multiple outer sleeves 11. By setting multiple reducing water flow resistance structures 13 on the upstream side of multiple outer sleeves 11, the stressed area subjected to the water impact of the outer sleeves 11 (the fixed pipes 12 are formed herein later) is greatly reduced, and the stability of the fixed pipes 12 formed later is greatly increased. As shown in FIG. 4, the reducing water flow resistance structures 13 are disposed on the very top and the bottom of the outer frame 1′. In this embodiment, the multiple reducing water flow resistance structures 13 and the body of the outer frame 1′ are integrally formed.

Take the four outer sleeves 11 in the second column from left in FIG. 4 as an example, as the outer sleeves 11 are arranged as one column parallel to the water flow direction, the flow impact force on the outer sleeves 11 located downstream is greatly reduced after the obstruction of the outer sleeves 11 located upstream. Experiments show that if there's no reducing water flow resistance structure 13, in the case that the current speed does not change, the sum of the flow impact forces on the four outer sleeves 11 is about 2.6 times of the flow impact force on one outer sleeve 11 exposed in the water. However, after disposing the reducing water flow resistance structure 13 at the outer frame 1′, the sum of the flow impact force on the four outer sleeves 11 is only 30% of the flow impact force on one outer sleeve 11 exposed in the water.

In the embodiment, the cross section of the reducing water flow resistance structures 13 is triangle. However, the detailed shape and the construction of the reducing water flow resistance structures 13 are not limited in the invention. In other embodiments, the reducing water flow resistance structures can be made streamlined.

In the embodiment, a tidal current energy generating device 200 includes six built-in modules, every built-in module has one inner frame 2, two corresponding horizontal-axis hydraulic generators 3, and three bearings 5′. However, this invention is not limited thereto. The number of the horizontal-axis hydraulic generators 3 in both the horizontal direction (the horizontal direction as shown in FIG. 4, namely the horizontal direction perpendicular to the water flow direction) and the vertical direction (the vertical direction as shown in FIG. 4, namely the depth direction perpendicular to the horizontal plane) can be increased according to the power generation demand of the tidal current energy generating device, so that the large scale of the tidal current energy generating device 200 can be realized

In the third embodiment, the bearing 5′ includes an inner ring 51′, an outer ring 52′, and a rolling element 53′. The inner ring 51′ is matched with the mounting shaft 4 and rotates with the mounting shaft 4, and the outer ring 52′ is matched with a bearing house 76′ as the support. The bearing 5′ changes the sliding fraction between the mounting shaft and the bearing inside the sliding bearing into the rolling friction of the rolling elements 53′ between the inner ring 51′ and the outer ring 52′.

In the embodiment, an underwater shaft rotating protecting device 7′ further comprises three bearing houses 76′, a lubricant cavity 75′ formed by two seal rings 72′, the bearing 5′, the bearing house 76′ and the mounting shaft 4, and the rolling elements 53′ of the bearing 5′ are located inside the lubricant cavity 75′. Specifically, the bearing house 76′ in the embodiment further includes two end caps 761′. The end cap 761′ cannot only have an axial positioning function for the bearing 5′, but also have the functions of preventing impurities and sealing with the seal ring 72′. A seal cavity is formed by the two end caps 761′ up and down, the seal rings 72′, the mounting shaft 4, and the bearing house 76′, and the bearing 5′ is located inside the cavity.

In the third embodiment, the lubricant is lubricating oil. A tube 73′ is communicated with the upper end cap 761′, and the other tube 73′ is communicated with the lower end cap 761′. By these settings, the rolling elements 53′ of the bearing 5′ are immersed in the lubricating oil.

Although the density of the lubricating oil is slightly less than that of the water, and the pressure is proportional to the density and the depth, as the height difference between the lubricant storage tank 71′ above the water surface and the underwater lubricant cavity 75′ is relatively large, after calculation, in general, the lubricant cavity 75′ is still in a state of “micro-positive pressure”. In other words, even if the lower seal rings 72′ cannot realize the sealing, the lubricant will also continually flow from the lubricant storage tank 71′ into the lubricant cavity 75′ due to the pressure difference action, and then flows from the gap to the outside of the seal ring 72′, and the outer water with sediments cannot flow into the lubricant cavity 75′ from the gap, so that the protection for the mounting shaft 4 can be truly achieved.

In the embodiment, the tidal current energy generating device 200 further includes at least four water flow deflectors 8, and every water flow deflector 8 is disposed corresponding to every horizontal-axis hydraulic generator 3. Every water flow deflector 8 has two water guiding sections 81 and one middle section 82. The middle section 82 is located between the two water guiding sections 81. A cross section 811 of one side of every water guiding section 81 far away from the middle section 82 is rectangular. A cross section 812 of one side of every water guiding section 81 connected with the middle section 82 is circular. A cross section 821 of the middle section 82 is circular. The cross sections 811, 812, and 821 are perpendicular to the horizontal plane and are perpendicular to a water flow direction D2, and the area of the circular cross sections 812 and 821 is smaller than that of the rectangular cross section.

In detail, the middle section 82 is a cylindrical tube, and one end of every water guiding section 81 is rectangular and is transited into the circular three-dimensional structure in the other end. The area of the circular cross section 812 of the water guiding section 81 is approximately equal to that of the circular cross section 821 of the middle section 82. The area of the circular cross section 812 of the water guiding section 81 is smaller than that of the rectangular cross section 811. In actual application, the horizontal-axis hydraulic generator 3 is just located inside the cylindrical middle section 82.

By setting one end of water guiding sections 81 to be a rectangle, seamless connection of the connecting end faces of the inner frame 2 can be realized. The existing tidal current generating device utilizes a water flow deflector of which all the cross sections are circular on the upstream side. Since the existing frames are all rectangular, a gap will exist between the circle and the rectangle during the installation. If there is nothing blocking the gap, when the tidal current impacts the hydro turbine, a considerable part of the current will flow into the hydro turbine from the gap, and even impact the back of the impeller blades, which greatly reduces the generated power. If the gap is blocked by a panel, the current will flow directly into the panel, generating a huge stress, which easily damages the structure of the entire frame. Especially, after blocking with the panel, the current direction will change or even the current flows everywhere, which terribly reduces the utilization ratio of the tidal current energy, thereby reducing the generated power.

By transiting from the rectangle to the circle with a smaller area, the water channel is narrowed, and the water flows are concentrated directed to the horizontal-axis hydraulic generator 3, so that the impeller 31 of the horizontal-axis hydraulic generator 3 is stressed more and the rotation speed is higher. Thus, the power generating efficiency is increased. In particular, both sides of the water flow deflector 8 are rectangular rather than being rectangular at one end. In this way, the water flow deflector 8 can achieve the flow guiding function regardless of the flood tide or the ebb tide.

The water flow deflectors 8 can be fixed to the outer frame 1′ or the inner frames 2. In the embodiment, the water flow deflectors 8 are all fixed to the inner frames 2. However, the invention is not limited thereto. In actual application, the water flow deflectors 8 can be installed separably, wherein the middle section 82 thereof can be fixed to the inner frame 2, and the two water guiding sections 81 can be fixed to the outer frame 1′. In the actual installation, the middle section 82 can be fixed above the water surface while assembling the built-in module, the water guiding sections 81 can be directly fixed to the outer frame 1′, and then when the built-in module is hung into the outer frame 1′, the assembly of the water flow deflector 8 is completed.

To sum up, the tidal current energy generating device in the invention can allow the generating device to be modularly assembled and replaced above the water surface by disposing separable inner frames and the outer frame, such that the costs of maintenance and installation can be greatly reduced, thereby overcoming the difficulties that the conventional ocean energy generating device cannot be commercialized and large-scale. Further, by disposing at least two horizontal-axis hydraulic generators and at least three bearings on the mounting shaft, the “multipoint restriction” is achieved for the mounting shaft, which makes the scale of the tidal current energy generating device can be extended not only in the horizontal direction (the horizontal direction perpendicular to the water flow) but also in the vertical direction (the depth direction perpendicular to the horizontal plane), such that the power generation efficiency is greatly improved and the problem that the existing ocean energy generating devices cannot “be large” and “be deep” is solved. By disposing the mounting shaft, the load of the generator can be innovatively adjusted by changing the orientation of the entire horizontal-axis hydraulic generator instead of individually changing the direction of the upstream angles of the blades, so that no matter how much the current speed is, the generator can always be guaranteed to be in a safe load and generate electricity, thereby greatly improving the power generation efficiency. More important, by disposing a rotatable mounting shaft, the impeller of the horizontal-axis hydraulic generator can always be turned towards the water flow regardless of the direction in which the water flows, thereby ensuring the maximum generating power, which is especially suitable for utilizing the tidal energy to generate power. In addition, the underwater shaft rotating protecting device provided by the invention can effectively protect the bearings from the outer impurities, especially preventing the sediments in the water from entering into the bearings, so as to effectively protect the normal operation of the bearings. By adopting the underwater shaft rotating protecting device, the tidal current energy generating device in the invention extends the service lives of the bearings, the maintenance frequency and maintenance costs are greatly reduced, and the power generating efficiency is ensured not to be affected at the same time. Furthermore, the bearing of the tidal current energy generating device provided by the invention can be a rolling bearing, which overcomes the technical barrier that only sliding bearing with water as the lubricant can be used for an underwater shafting in the prior art.

Moreover, by setting the detection module, whether the sealing of the bearings is reduced or not can be known intuitively and timely, which effectively guides the maintenance personnel when and where to maintain, thereby improving the promptness and reliability of the maintenance. In addition, since the frame includes separable outer frame and inner frame, the underwater shaft rotating protecting device can be maintained or replaced conveniently and quickly, and the maintenance cost is greatly reduced.

By disposing the water flow deflectors, the water flows are all concentrated to the horizontal-axis hydraulic generator, making the impeller of the horizontal-axis hydraulic generator subject to a larger force and rotate faster, and thus the power generation efficiency is improved. The water flow deflector provided by the embodiments of the invention is rectangular at the two ends and circle in the middle, and it can always achieve the flow guiding function regardless of the flood tide or the ebb tide. Further, the water flow deflector with a specific structure has a better flow guiding effect.

Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, the disclosure is not for limiting the scope of the invention. Persons having ordinary skill in the art may make various modifications and changes without departing from the scope and spirit of the invention. Therefore, the scope of this invention is subject to the scope of the claims. 

What is claimed is:
 1. A tidal current energy generating device, comprising: an outer frame; at least two inner frames, separably disposed in the outer frame; at least two mounting shafts, rotatablely disposed in the two inner frames, respectively, an axial direction of the at least two mounting shafts being perpendicular to a horizontal plane; a driving unit, connected with the at least two mounting shafts to drive the mounting shafts to rotate; at least four horizontal-axis hydraulic generators, every two horizontal-axis hydraulic generators fixed at one mounting shaft and disposed in the same inner frame, and the at least four horizontal-axis hydraulic generators changing directions with the rotating of the driving unit; and at least six bearings, every three bearings sleeved on one mounting shaft, and the three bearings on one mounting shaft disposed on the two sides of the two horizontal-axis hydraulic generators and between the two horizontal-axis hydraulic generators, respectively.
 2. The tidal current energy generating device according to claim 1, further comprising at least four water flow deflectors, wherein every water flow deflector is disposed corresponding to every horizontal-axis hydraulic generator, the at least four water flow deflectors are fixed at the outer frame or the inner frames, every water flow deflector has two water guiding sections and one middle section, the middle section is located between the two water guiding sections, a cross section of one side of every water guiding section far away from the middle section is rectangular, a cross section of one side of every water guiding section connected with the middle section is circular, a cross section of the middle section is circular, the cross sections are perpendicular to the horizontal plane and are perpendicular to a water flow direction, and the area of the circular cross section is smaller than that of the rectangular cross section.
 3. The tidal current energy generating device according to claim 1, further comprising an underwater shaft rotating protecting device, wherein the underwater shaft rotating protecting device comprises: a lubricant storage tank, wherein a lubricant is stored and the lubricant storage tank is disposed above water surface; at least six seal rings, every two seal rings corresponding to one bearing and sleeved on the mounting shaft, and a lubricant cavity being formed between every two seal rings and the corresponding bearing and the mounting shaft; and a tube, one end of the tube is communicated with the lubricant storage tank, and the other end communicated with the lubricant cavity.
 4. The tidal current energy generating device according to claim 3, wherein the underwater shaft rotating protecting device further comprises a detection module, disposed at the lubricant storage tank to detect whether the lubricant is reduced or not.
 5. The tidal current energy generating device according to claim 3, wherein the bearing is a sliding bearing, and every lubricant cavity is formed by two seal rings, the bearing, and the mounting shaft.
 6. The tidal current energy generating device according to claim 3, wherein the bearing is a rolling bearing, the underwater shaft rotating protecting device further comprises at least three bearing houses, and each lubricant cavity is formed by two seal rings, the bearing, the bearing house, and the mounting shaft.
 7. The tidal current energy generating device according to claim 1, wherein the outer frame has a plurality of fixed piles, and the outer frame is fixed at the sea bottom through piling.
 8. The tidal current energy generating device according to claim 1, wherein the outer frame has a plurality of reducing water flow resistance structures. 